Children who use cell phones are at no greater risk of developing brain tumors, the latest paper in a series of epidemiological studies suggests.

The study, which was conducted in Norway, Denmark, Sweden, and Switzerland, was recently published in the Journal of the National Cancer Institute. It surveyed almost 1,000 children between ages 7 and 19. The group looked at children who had been diagnosed with brain tumors between 2004 and 2008, as well as a control group drawn randomly from the general population.

Subjects were asked about how often they used their cell phones for voice calls. Some information about usage was provided by wireless providers when it was available. Researchers concluded that children who regularly used their cell phones did not have a higher risk of developing brain tumors than children who didn't use cell phones regularly. There was also no increased risk of brain tumors in the areas of the head that likely received the most exposure from cell phones.

As cell phone use among children and adolescents increases, experts have warned that they may be at greater risk for cancer and brain tumors. One reason for concern is the fact that children who start using cell phones at a young age will inevitably have more exposure over their entire lifetime to cell phone radiation. But researchers are also concerned because children's nervous systems are not fully developed. Also, their brains contain more fluid than brains of adults, which allows for deeper penetration of radiation. And finally, children's skulls are not as thick as those of adults. And again, studies indicate that children are likely to absorb more radiation from cell phones.

While radiation from cell phones may actually penetrate further into the brains of children, it's not known whether that radiation causes damage to cells. Cell phones emit non-ionizing radiation that propagates at much lower frequency than ionizing radiation, such as X-rays, which are also known to damage DNA in cells.

Some animal research suggests there may be some cell damage done at low frequency radiation. And a recent study on humans found that cell phone radiation excited brain activity.

But what is still unknown is what long-term health effects this may have on people who use cell phones regularly over a long period of time. Epidemiological studies, including the World Health Organization's decade long Interphone study, have generally shown no relation between cell phone use and brain cancer. But the data from the Interphone study is still being examined, and more reports are expected using this data.

A series of reports have come out recently again showing no link between cancer or brain tumors and cell phone use.

Still, the World Health Organization's International Agency for Research on Cancer (IARC) in May categorized cell phone usage as a possible carcinogen, putting it in the same category as lead, gasoline engine exhaust, and chloroform. While recent studies show no link between cell phone use and brain tumors, the WHO and other scientists have said there is enough conflicting evidence to suggest that more research is needed.

This most recent study published in the Journal of the National Cancer Institute is among the first to examine the effects of cell phone use on children. But even Martin Roosli, lead author of the study and an epidemiologist at the Swiss Tropical and Public Health Institute in Basel, told The Wall Street Journal that researchers should still keep an eye on how cell phone use affects children.

As with most epidemiological studies there can be an inherent bias when subjects who already have brain tumors are asked about their usage. What's more, brain tumors typically take decades to manifest, which means that exposure in childhood to cell phones could lead to health effects later in life. Also, the length of time that most children in the study had been exposed to cell phones was relatively short.

About the author

Marguerite Reardon has been a CNET News reporter since 2004, covering cell phone services, broadband, citywide Wi-Fi, the Net neutrality debate, as well as the ongoing consolidation of the phone companies. E-mail Maggie.
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